JP2008309947A - Imaging apparatus and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce consumption power by efficiently using C-AF (Continuous Automatic Focus). <P>SOLUTION: On the basis of outputs from a yaw direction angular velocity sensor 42 and pitch direction angular velocity sensor 43, an angular velocity detection circuit 44 calculates an angular velocity. On the basis of the angular velocity, a shake width detection circuit 45 continuously detects the amounts of shake of the device. If the maximum value of the latest amount of shake between the Nmses is smaller than a prescribed value, the judgement is made that the timing of a photographing operation is about to take place, and the C-AF is operated. If the maximum value of the latest shake width between the Nmses is equal to or greater than the prescribed amount, the judgement is made that the photographing operation is not carried out, and the C-AF is stopped. By operating the C-AF only when necessary, consumption power can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus and an image pickup method, and more particularly to an image pickup apparatus and an image pickup method for detecting a camera shake and controlling the operation and non-operation of continuous AF.

  In an autofocus (AF) camera such as a digital camera, an AF operation is performed only when the release button is half-pressed, and once in focus, the in-focus state is maintained until the half-press is released. There is known a camera capable of switching between two modes of the S-AF mode) and a so-called continuous AF mode (C-AF mode) in which the AF operation is always continuously repeated regardless of half-pressing. In the C-AF mode, when the focus evaluation value decreases after focusing, the AF operation is started again, the focus lens is moved by a predetermined amount, and the evaluation value increases by comparing the magnitude of the focus evaluation value before and after the movement. The same processing is performed by moving a predetermined amount further in the direction. Then, by repeatedly executing such processing, the focus lens is moved to a position where the focus evaluation value reaches a peak.

This C-AF mode is used to follow a moving subject and reduce the time lag at the time of shooting. However, as described above, since the focus lens is always driven to perform a focusing operation, there is a disadvantage that power consumption is large. there were. In order to eliminate this drawback, Patent Document 1 describes a camera that changes the range of the evaluation value range for restarting after focusing once and performing focusing again depending on the subject and shooting conditions. ing. According to the camera described in Patent Document 1, it is possible to reduce wasteful power consumption by reducing the restart frequency of C-AF.
JP 2003-107326 A

  However, even in the camera described in Patent Document 1, the C-AF operates even when the photographer performs camera work such as the position, angle, and photographing size with respect to the subject. There was a drawback of doing. The present invention has been made in view of such circumstances, and an object thereof is to provide an imaging apparatus and an imaging method capable of efficiently reducing power consumption by using C-AF.

  In order to achieve the object, the imaging apparatus according to claim 1, an imaging unit that converts a subject image received through the imaging lens into an image signal, and a focus lens is moved to a focus position based on the image signal. Automatic focusing means, control means for continuously operating the automatic focusing means, and shake detection means for continuously detecting shake of the apparatus main body, the control means detected by the detection means The automatic focusing means is operated when the latest shake during a predetermined period is less than a predetermined amount, and the operation of the automatic focusing means is stopped when the shake is more than a predetermined amount.

  Thereby, C-AF can be used efficiently and power consumption can be suppressed.

  According to a second aspect of the present invention, in the imaging apparatus according to the first aspect of the present invention, the image capturing apparatus includes an input unit that allows a user to set shooting parameters, and the input unit can set the predetermined amount.

  As a result, an easy-to-use C-AF can be realized.

  According to a third aspect of the present invention, in the imaging apparatus according to the first or second aspect, the input unit can set the predetermined period.

  As a result, an easy-to-use C-AF can be realized.

  In order to achieve the above object, an imaging method according to claim 4, wherein an imaging process for converting a subject image received through an imaging lens into an image signal, and a focus lens is moved to a focus position based on the image signal. An automatic focusing step, a control step for continuously operating the automatic focusing step, and a shake detection step for continuously detecting shake of the apparatus main body, wherein the control step is detected by the detection step. The automatic focusing step is operated when the latest shake for a predetermined period is less than a predetermined amount, and the automatic focusing step is stopped when the amount is more than a predetermined amount.

  Thereby, C-AF can be used efficiently and power consumption can be suppressed.

  According to the present invention, it is possible to provide an imaging apparatus and an imaging method capable of efficiently reducing the power consumption by using the C-AF by detecting the amount of camera shake and controlling the operation and non-operation of the C-AF. be able to.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a block diagram showing an electrical configuration of a first embodiment of a digital camera to which the present invention is applied.

  As shown in the figure, the digital camera 10 of the present embodiment includes a CPU 11, an operation unit 12, a zoom lens motor driver 13, a zoom lens 14, a focus lens motor driver 15, a focus lens 16, and a camera shake correction control unit. 17, camera shake correction lens 18, timing generator 19, CCD driver 20, CCD 21, analog signal processing unit 22, A / D converter 23, image input controller 24, image signal processing circuit 25, compression processing circuit 26, video encoder 27 , An image display device 28, a bus 29, a media controller 30, a recording medium 31, a memory (SDRAM) 32, an AF detection circuit 33, an AE detection circuit 34, and the like.

  Each unit operates under the control of the CPU 11, and the CPU 11 controls each unit of the digital camera 10 by executing a predetermined control program based on an input from the operation unit 12.

  The CPU 11 has a built-in program ROM, in which various data necessary for control are recorded in addition to the control program executed by the CPU 11. The CPU 11 controls each unit of the digital camera 10 by reading the control program recorded in the program ROM into the memory 32 and sequentially executing the program.

  The memory 32 is used as a program execution processing area, a temporary storage area for image data, and various work areas.

  The operation unit 12 includes general camera operation means such as a power switch, a release button, a shooting mode dial, and a camera shake correction switch, and outputs a signal corresponding to the operation to the CPU 11.

  The focus lens 16 is driven by the focus lens motor driver 15 to move back and forth on the optical axis of the zoom lens 14. The CPU 11 controls the movement of the focus lens 16 via the focus lens motor driver 15 to perform focusing.

  The zoom lens 14 is driven by the zoom lens motor driver 13 to move back and forth on the optical axis of the focus lens 16. The CPU 11 controls the movement of the zoom lens 14 via the zoom lens motor driver 13 to perform zooming.

  The camera shake correction lens 18 is controlled by the camera shake correction control unit 17 so as to cancel the camera shake in each of two orthogonal directions within the lens surface, and the camera shake of the subject image via the zoom lens 14 and the focus lens 16 is controlled. And the subject image after the camera shake correction is transmitted to the CCD 21.

  The CCD 21 is disposed after the camera shake correction lens 18 and receives subject light transmitted through the camera shake correction lens 18. As is well known, the CCD 21 has a light receiving surface on which a large number of light receiving elements are arranged in a matrix. The subject light transmitted through the camera shake correction lens 18 is imaged on the light receiving surface of the CCD 21 and converted into an electric signal by each light receiving element.

  The CCD 21 outputs the charge accumulated in each pixel as a serial image signal line by line in synchronization with the vertical transfer clock and horizontal transfer clock supplied from the timing generator 19 via the CCD driver 20. The CPU 11 controls the timing generator 19 to control the driving of the CCD 21.

  Note that the charge accumulation time (exposure time) of each pixel is determined by an electronic shutter drive signal given from the timing generator 19. The CPU 11 instructs the timing generator 19 on the charge accumulation time.

  The output of the image signal is started when the digital camera 10 is set to the shooting mode. That is, when the digital camera 10 is set to the photographing mode, output of an image signal is started to display a through image on the image display device 28. The output of the image signal for the through image is temporarily stopped when the instruction for the main photographing is given, and is started again when the main photographing is finished.

  The image signal output from the CCD 21 is an analog signal, and this analog image signal is taken into the analog signal processing unit 22.

  The analog signal processing unit 22 includes a correlated double sampling circuit (CDS) and an automatic gain control circuit (AGC). The CDS removes noise contained in the image signal, and the AGC amplifies the noise-removed image signal with a predetermined gain. The analog image signal subjected to the required signal processing by the analog signal processing unit 22 is taken into the A / D converter 23.

  The A / D converter 23 converts the captured analog image signal into a digital image signal having a gradation width of a predetermined bit. This image signal is so-called RAW data, and has a gradation value indicating the density of R, G, and B for each pixel.

  The image input controller 24 has a built-in line buffer having a predetermined capacity, and stores the image signal for one frame output from the A / D converter 23. The image signal for one frame accumulated in the image input controller 24 is stored in the memory 32 via the bus 29.

  In addition to the CPU 11, memory 32, and image input controller 24, the image signal processing circuit 25, compression processing circuit 26, video encoder 27, media controller 30, AF detection circuit 33, AE detection circuit 34, etc. are connected to the bus 29. These are configured to be able to transmit and receive information to and from each other via a bus 29.

  The image signal for one frame stored in the memory 32 is taken into the image signal processing circuit 25 in a dot sequence (pixel order).

  The image signal processing circuit 25 performs predetermined signal processing on the image signals of R, G, and B colors captured in a dot-sequential manner, and generates an image signal (Y / C) composed of a luminance signal Y and color difference signals Cr, Cb. Signal).

  The AF detection circuit 33 fetches R, G, B image signals stored in the memory 32 via the image input controller 24 in accordance with a command from the CPU 11 and calculates a focus evaluation value necessary for AF (Automatic Focus) control. . The AF detection circuit 33 includes a high-pass filter that passes only a high-frequency component of the G signal, an absolute value processing unit, a focus region extraction unit that extracts a signal within a predetermined focus region set on the screen, and a focus region An integration unit for integrating the absolute value data is included, and the absolute value data in the focus area integrated by the integration unit is output to the CPU 11 as a focus evaluation value. During the AF control, the CPU 11 searches for a position where the focus evaluation value output from the AF detection circuit 33 is maximized, and moves the focus lens 16 to that position, thereby performing focusing on the main subject.

  The AE detection circuit 34 takes in R, G, and B image signals stored in the memory 32 via the image input controller 24 in accordance with a command from the CPU 11 and calculates an integrated value necessary for AE control. The CPU 11 calculates a luminance value from the integrated value and obtains an exposure value from the luminance value. Further, the aperture value and the shutter speed are determined from the exposure value according to a predetermined program diagram.

  The compression processing circuit 26 performs compression processing of a predetermined format (for example, JPEG) on the input image signal (Y / C signal) composed of the luminance signal Y and the color difference signals Cr and Cb in accordance with the compression command from the CPU 11. Generate compressed image data. Further, in accordance with a decompression command from the CPU 11, the input compressed image data is subjected to decompression processing in a predetermined format to generate non-compressed image data.

  The video encoder 27 controls display on the image display device 28 in accordance with a command from the CPU 11.

  The media controller 30 controls reading / writing of data with respect to the recording medium 31 in accordance with a command from the CPU 11. The recording medium 31 may be detachable from the camera body such as a memory card, or may be built in the camera body. In the case of detachable, a card slot is provided in the camera body, and the card slot is used by being loaded.

  Next, the camera shake correction control unit 17 will be described. FIG. 2 is a block diagram showing the camera shake correction control unit 17 and its peripheral part.

  The camera shake correction control unit 17 includes a position detection circuit 41, a yaw direction angular velocity sensor 42, a pitch direction angular velocity sensor 43, an angular velocity detection circuit 44, a shake width detection circuit 45, a camera shake correction control circuit 46, and a drive circuit 47. The The camera shake correction lens 18 includes an X axis actuator 18a and a Y axis actuator 18b for moving the camera shake correction lens 18, and an X axis Hall element 18c and a Y axis Hall element for detecting the position of the camera shake correction lens 18. 18d.

  The angular velocity detection circuit 44 continuously detects the angular velocity of the digital camera 10 based on the outputs of the yaw direction angular velocity sensor 42 and the pitch direction angular velocity sensor 43. 6A is a diagram showing the output of the pitch direction angular velocity sensor 43, and FIG. 6B is a diagram showing the output of the yaw direction angular velocity sensor 42. As shown in FIG. As described above, the angular velocity sensor outputs a DC voltage with a constant bias when stationary, and when the sensor rotates, a DC voltage corresponding to the angular velocity is added to the bias voltage and output. The angular velocity detection circuit 44 calculates an angular velocity based on the sensor outputs in the two directions.

  The camera shake correction control circuit 46 can drive the camera shake correction lens 18 by driving the X-axis actuator 18 a and the Y-axis actuator 18 b via the drive circuit 47. The position detection circuit 41 can detect the position of the camera shake correction lens 18 based on the outputs of the X-axis Hall element 18c and the Y-axis Hall element 18d. Based on the position information output from the position detection circuit 41, the camera shake correction control circuit 46 moves the camera shake correction lens 18 by a control amount corresponding to the angular velocity calculated by the angular velocity detection circuit 44, and performs camera shake correction. Do.

  At this time, the blur width detection circuit 45 monitors the fluctuation amount of the angular velocity calculated by the angular velocity detection circuit 44 and outputs the blur amount to the CPU 11. The CPU 11 controls the AF operation for the focus lens 16 based on the input blur amount.

  Here, the control of the AF operation based on the blur amount will be described. FIG. 3 is a flowchart showing the control of the AF operation in the digital camera 10.

  When the power is turned on to the digital camera 10, the amount of blur is continuously detected (step S301). As described above, the blur width detection circuit 45 monitors the fluctuation amount of the angular velocity calculated by the angular velocity detection circuit 44 and outputs the blur amount to the CPU 11. Next, the AF mode is determined (step S302). The digital camera 10 according to the present invention has two AF modes, S-AF and C-AF, and can be selected by the photographer using the operation unit 12. If it is set to the S-AF mode, the detected blur amount is not determined, and the process proceeds to step S305, where C-AF is turned off. When the C-AF mode is set, it is determined whether or not the maximum blur amount detected in step S301 is less than a predetermined amount for the latest Nms (step S303). When it is determined that the maximum value of the blur amount is less than the predetermined amount for the latest Nms, the C-AF operation is performed (step S304), and when it is determined that the maximum value of the blur amount is equal to or greater than the predetermined amount. C-AF is not performed. The blur amount detection and C-AF control will be described with reference to FIGS.

4A is a diagram showing the output of the pitch direction angular velocity sensor 43, and FIG. 4B is a diagram showing the output of the yaw direction angular velocity sensor 42. As shown in FIG. Here, from time t ₁ to time t ₂ , the change in the angular velocity is large in both the pitch direction and the yaw direction, indicating that the state is unstable. This state is a state in which no photographing operation is performed, such as the photographer holding the digital camera 10 with one hand. Further, at time t ₄ from the time t _3, and the change of the angular velocity in the pitch and yaw directions both becomes small, this state continues Nms. This is a state in which the photographer holds the digital camera 10 and performs a photographing operation.

Similarly, FIG. 5A is a diagram showing the output of the pitch direction angular velocity sensor 43, and FIG. 5B is a diagram showing the output of the yaw direction angular velocity sensor 42. From time t ₅ to time t ₇ , the change in angular velocity in the pitch direction is large, and the photographer is in a state of tilting the digital camera 10. Further, at time t ₈ from the time t _6, a large change in the yaw direction of the angular velocity, a state where the photographer is panning the digital camera 10. These are states in which the photographer is searching for an angle. Then, at time t ₉ from the time t _8, and the change of the angular velocity in the pitch and yaw directions both becomes small, this state continues Nms. This is a state in which the photographer holds the digital camera 10 and performs a photographing operation.

Thus, it can be seen that the angular velocity sensor when the photographer performs camera work has a feature that the amplitude of the output signal is large and the amplitude of the angular velocity sensor output signal becomes small when the camera work is finished. Therefore, it is possible to predict the timing at which the photographing operation is performed by monitoring the blur amount using the angular velocity sensor. In the C-AF mode in the digital camera 10 of the present embodiment, the C-AF operation is performed when it is predicted that the timing for performing the shooting operation is performed. That is, when the latest angular velocity sensor output width between Nms is GyroW _Nms and the C-AF operation threshold is GyroW_Thresh, C-AF is operated only when GyroW _Nms ≦ GyroW_Thresh is satisfied, The C-AF operation is not performed.

  Next, it is determined whether or not the release button of the operation unit 12 has been pressed halfway (step S306). If the release button has not been pressed halfway, the process returns to step S301.

  When the release button is half-pressed, the CPU 11 operates the AE detection circuit 34, and determines the aperture value and the shutter speed from the obtained exposure value (step S307). Next, the AF mode is determined. If it is set to S-AF, focus lock is performed (step S310). If it is set to C-AF, the focusing operation is performed based on information before the release button is half-pressed. Continue (step S309).

  Thereafter, when the release button is fully pressed (step S311), actual shooting is performed (step S312), and the shot image is recorded on the recording medium 31 (step S313).

  In this way, by calculating the shake amount from the angular velocity sensor and controlling the C-AF based on the calculated shake amount, it is possible to suppress useless C-AF operation and reduce power consumption.

  In this embodiment, the C-AF operation is performed when the amount of blur during the latest predetermined period (Nms) is less than the predetermined amount (GyroW_Thresh). It may be a value set in the digital camera 10 or may be set by the photographer through the operation unit 12. Similarly, GyroW_Thresh, which is a blur amount threshold value, may be a value set in advance in the digital camera 10 or may be set by the photographer through the operation unit 12.

  In the present embodiment, the C-AF is operated when the outputs of both the yaw direction angular velocity sensor 42 and the pitch direction angular velocity sensor 43 are stable. The C-AF may be operated when one output is stable.

FIG. 1 is a block diagram showing an electrical configuration of a first embodiment of a digital camera to which the present invention is applied. FIG. 2 is a block diagram showing the camera shake correction control unit 17 and its peripheral part. FIG. 3 is a flowchart showing the AF operation in the digital camera 10. FIG. 4 is a diagram illustrating outputs of the pitch direction angular velocity sensor 43 and the yaw direction angular velocity sensor 42. FIG. 5 is a diagram illustrating outputs of the pitch direction angular velocity sensor 43 and the yaw direction angular velocity sensor 42. FIG. 6 is a diagram illustrating the outputs of the pitch direction angular velocity sensor 43 and the yaw direction angular velocity sensor 42.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Digital camera, 11 ... CPU, 12 ... Operation part, 15 ... Focus lens motor driver, 16 ... Focus lens, 17 ... Camera shake correction control circuit, 18 ... Camera shake correction lens, 21 ... CCD, 22 ... Analog signal Processing circuit, 23 ... A / D converter, 24 ... Image input controller, 25 ... Image signal processing circuit, 26 ... Compression processing circuit, 32 ... Memory, 33 ... AF detection circuit, 34 ... AE detection circuit

Claims (4)

Imaging means for converting a subject image received through the imaging lens into an image signal;
Automatic focusing means for moving the focus lens to a focus position based on the image signal;
Control means for continuously operating the automatic focusing means;
A shake detecting means for continuously detecting the shake of the apparatus main body,
The control means operates the automatic focusing means when the latest blur of the predetermined period detected by the detection means is less than a predetermined amount, and stops the operation of the automatic focusing means when the fluctuation is greater than a predetermined amount. An imaging apparatus characterized by the above.   The imaging apparatus according to claim 1, further comprising an input unit that allows a user to set shooting parameters, wherein the input unit can set the predetermined amount.   The imaging apparatus according to claim 1, wherein the input unit can set the predetermined period. An imaging process for converting a subject image received through an imaging lens into an image signal;
An automatic focusing step of moving the focus lens to a focusing position based on the image signal;
A control step of continuously operating the automatic focusing step;
A shake detection step for continuously detecting the shake of the apparatus main body,
The control step operates the automatic focusing step when the blur of the latest predetermined period detected by the detection step is less than a predetermined amount, and stops the operation of the automatic focusing step when the amount is more than a predetermined amount. An imaging method characterized by the above.

Images